Hollywood, CA—A recent joint meeting of the SMPTE Hollywood and AES Los Angeles sections took a deep dive into translating theatrical movie soundtracks for home listening. Produced by Lon Neumann, principal, Immersive Audio Alliance, the program, Preparing Movie Soundtracks for the Home Environment: It’s Complicated!, included presentations from Floyd Toole, Ph.D., JBL vice president, acoustical engineering (retired); Brian Vessa, executive director of audio mastering, Sony Pictures; and Scott Kramer, Netflix’s manager of sound technology.
Neumann kicked off the proceedings with a primer on the recommendations for the correct configuration and alignment of a critical listening environment, including the ATSC A/85:2013 document. “It’s still the best collection of useful guidance on this topic,” said Neumann.
One issue associated with mixing cinema content for home listening is the difference in monitoring calibration levels between the two environments, which vary significantly in physical volume. Consequently, said Neumann, cinema mixing spaces are calibrated at 85 dBSPL, while A/85 recommends 76 or 78 dB for smaller spaces, depending on the exact dimensions. “We hear differently at different levels, and we know that consumers are going to be listening at substantially lower levels,” he said.
Neumann also talked about the importance of metadata in Dolby encoding, especially the dialnorm settings. He added, “Dynamic range control keeps people happy when it’s working as intended. It’s in the metadata, so it’s there to be used, if you want—but you don’t have to use it.”
Nuts and Bolts
Floyd Toole talked about the “nuts and bolts of audio,” as he described them. “My focus has been sound quality, because without high-quality sound, nothing can be truly pleasurable,” he said, launching into a review of some of the metrics behind room acoustics and loudspeaker performance.
Any industry needs standards, he said, and two standards—SMPTE 202M and ISO 2969—were created for cinema audio. The X Curve, describing the target response of the cinema B-chain, is part of those standards. A lot of science went into the development of the X Curve, and subsequent research demonstrates that theaters largely conform to it.
“But things change,” Toole said, noting that content created for cinemas is now routinely watched on handheld devices and in the home. “There’s an enormous audience not addressed by the movie standard. This is the difficulty; it needs to be addressed.”
Demonstrating the correlation between frequency response in large and small rooms, he noted that any differences are explainable by physics. “The difference between them at high frequencies is totally air absorption,” he said, adding that cinemas have much higher reverberation times, so the bass is going to rise. To arrive at the flat X Curve target, “You’ve got to turn the bass down,” he continued, arguing instead that “a little too much bass is one of those forgivable sins.”
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Two ears and a brain are wonderful at extracting the essence of truth from complicated circumstances, said Toole, and they seem to extract and recognize something important in the direct, first-arrived sound, whatever the listening environment. “It should be neutral, flat and smooth. The X Curve method does not do this. Standardization is essential, but compatibility with all of the audience would seem to be a worthwhile objective. We’re simply not there yet.”
Theatrical Mixes in the Home
Brian Vessa went into great detail about why a theatrical mix is not suitable for home consumption, ran down the gear and process he uses for home mixes, noted the challenges of reproducing immersive sound in home environments, described remixing and upmixing for the immersive home theater, and offered a sample soundtrack delivery workflow.
The objective of the home theater process is to translate mixing intent into a smaller space with lower playback volume and a smaller visual image, he said. It’s nice to be able to fine-tune a mix for the home; it’s a creative process, not an automated one. For a new movie, this should be part of the production process, using the mixer who worked on the theatrical version and who is intimately familiar with every aspect of it, said Vessa.
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Subtle changes are going to have little impact in the home, he said, “so don’t be shy.” It’s not unusual for him to upmix elements to add immersive impact while retaining the original intent—a value-add, he said.
Freedom and Responsibility
Netflix is now the 800-pound gorilla in the world of media creation. Scott Kramer began by stressing the company’s core values: freedom and responsibility. “Our goal is to inspire people rather than manage them,” he said. “We trust our teams to do what they think is best for Netflix.”
That extends to the directors, showrunners and creatives Netflix works with, he said. “We believe they will feel a responsibility, not to us, per se, but to their fans, to deliver a sound mix, in this case, that will translate really well in the home.”
What most content has in common on the Netflix platform is dialogue, said Kramer. People adjust for comfortable dialogue, he added, noting that Netflix really has only two key nearfield mixing specs: loudness is -27 LKFS +/-2 LU dialogue gated, and peaks may not exceed 12 dBFS, so as not to create distortion in the decoder. The rest of the Netflix spec refers to organization of the content.
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There is no theatrical sound spec: “You do whatever you need to do. There’s total freedom,” said Kramer.
There are few enforced rules, but Netflix publishes guidance and best practices for sound mixes, he continued. Immersive audio is preferred as a top-level audio master. Dolby Atmos in a 9.1.6 configuration is encouraged, enabling mixers to use the proscenium effect to pull things off the screen and widen the front soundstage. A minimum 7.1.4 is required for QC, he added.
If there is no theatrical release, then a small to medium nearfield mix stage, “like a large living room,” is optimal, he said. There is no reason to set up an additional nearfield array around the console; the in-wall speakers in most TV mix rooms work just fine, he said.
Netflix has no X Curve engaged when reviewing mixes from around the world, “so we can hear everything that’s streaming,” he said, “and not lose any of those high frequencies.”
Overall, he summarized, the recommendation is to spend the budget with more days mixing in smaller rooms to perfect the experience. That said, a growing number of Netflix films are destined for theatrical release, where it makes sense to mix in a large room, followed by a week or so in a smaller room for the nearfield mix. “But in many cases, mix the nearfield first and then theatrical later,” said Kramer. “This is something we’re starting to think about if there’s no big theatrical release.”
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